In reference to your second statement though, I also dont always carry my laptop but it doesn't matter because my spreadhseets are in onedrive too, so I can close my laptop and open my phone and have the same spreadsheet with zero thought.
https://support.microsoft.com/en-us/office/define-and-solve-...
> For example, you can change the amount of your projected advertising budget and see the effect on your projected profit amount.
I can do this without Solver.
For example, let's say you have a spreadsheet to calculate the capacity of a steel column based on its height and cross-section/material. If you wanted to run the calculation backward and find the height that will give you a very specific capacity, you could do it manually by playing with the height until you find it or you can let Excel do it for automatically with the solver.